The present invention relates to data communications equipment and data terminal equipment In particular, this invention relates to the use of the interface between the data communications equipment and the dam terminal equipment.
Currently, there are a number of communications networks that are built around the 208B type of data communications equipment, or modem, which transfers data via a half-duplex signaling scheme at a transmission speed of 4800 bits per second (sec.). One example of such a communications network is the Electronic Data Interchange (EDI) network, which may be used by a business to distribute billing and inventory to its various locations, In addition, some states provide a half-duplex communications network to allow insurance carders to gain access to a state's division of motor vehicles data base to get information on licensed drivers within a state.
However, the 208B type of modem has been around for a long time and in comparison to a state-of-the-art modem, like the V.32 modem, it has a lower data throughput For example, the V.32 modem can transfer data via a full-duplex signaling scheme and has a transmission speed of 9600 bits per second. Unfortunately, a V.32 type of modem will not connect to a 208B modem. As a result, customer's who have networks comprising 208B modems can only upgrade to a V.32 type of modem by changing out their entire network of modems--at a large cost.
There have been some attempts in the prior art to deal with communications networks comprising different types of modems. One manufacturer sells a modem that can provide either a 208B mode of operation or a V.32 mode of operation. However, the particular mode of operation of this modem is determined by the adjustment of a hardware strap. In other words, the customer must physically access the modem and change a switch setting on the modem. Consequently, this requires that the mode of operation must be determined before even attempting to establish a connection to another modem. Therefore, the customer must know ahead of time the identity of the other modem, i.e., whether it is a 208B type of modem or a V.32 type of modem. While this may be feasible for originating a data call to another modem, this may not be a practical for answering a data call from another modem.
The co-pending commonly assigned United States application of R. E. Scott entitled "Half-Duplex or Full-Duplex Automode Operation for use in Data Communications Equipment," Ser. No. 07/978,536, filed on Nov. 17, 1992, now U.S. Pat. No. 5,349,635 which is hereby incorporated by reference, discloses a technique for overcoming the requirement of having to manually set the data communications equipment to either a half-duplex mode or a full-duplex mode of operation. Specifically, the Scott patent application teaches the notion of automatically switching between either a 208B, i.e., half-duplex, mode or a V.32 i.e., full-duplex, mode of operation within the data communications equipment.
Unfortunately, even if the data communications equipment automatically switches between a full-duplex mode or a half-duplex mode of operation, its respective data terminal equipment cannot automatically switch between these modes. In other words, irrespective of the data communications equipment mode of operation, the data terminal equipment must be manually configured to either a half-duplex mode or a full-duplex mode of operation. For example, if both the data communications equipment and the data terminal equipment are set for half-duplex operation and then the data communications equipment automatically switches to full-duplex operation, the data terminal equipment is still left operating in a half-duplex mode. In other words, the data terminal equipment is no longer synchronized to the operating mode of the data communications equipment. Consequently, the respective user of the data terminal equipment is not receiving the full benefit of full-duplex operation, which can provide two times the data throughput of half-duplex operation.